Vitamin D is a hormone-like fat-soluble micronutrient that affects our total-body health, including our bones and teeth, muscles, immune function, and much more. We acquire vitamin D through our dietary intake, or our bodies can synthesize vitamin D3 from cholesterol and UVB sun exposure.

Most adult Americans do not consume proper amounts of vitamin D through their diet, with reports showing that as much as 93% of the adult population in the US consume less than 400 IU vitamin D per day (1). This is where supplementation can be of benefit, especially if you choose the right form of vitamin D.

Vitamin D supplements come in 2 varieties – vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D3 is almost always animal-derived, from cholesterol obtained from sheep's wool lanolin. This is a good source of D3 and the most commonly available in the market today. In contrast, vitamin D2 is plant derived, and was developed in the 1920s by irradiating ergosterol from the mold ergot. Recent advances in technology over the past several years have developed vitamin D3 options from plant origins, which may be preferred by some vegetarians.

Vitamin D2 and D3 are both found in food sources such as irradiated yeast and mushrooms for D2, and egg yolk, oily fish and fish liver oils for D3. Some foods, such as dairy, orange juice, and breakfast cereals are fortified with vitamin D.  Vitamins D2 and D3 are also present in dietary supplements, although D3 is more common.

Vitamin D2 was originally patented and licensed to pharmaceutical companies in the 1920s, leading to the development of a medicinal preparation of vitamin D2 called Viosterol (2). Today, vitamin D2 is still the form found in the prescription medication form of vitamin D, usually available in 50,000 IU capsules.

For years, the two different forms of vitamin D were considered equivalent and interchangeable, however, this was based on studies of rickets prevention in infants conducted about 100 years ago.

Vitamin D3 is better at raising total 25-OH vitamin D levels (a storage form and marker of vitamin D status) than vitamin D2 (3). In some reports by as much as 87% more! (4).

Vitamin D3 is more stable than D2, lasting longer in the body due to a significantly longer half-life than D2 (5).

Vitamin D3 is superior to vitamin D2 in helping us achieve and maintain adequate vitamin D levels. This has been demonstrated through several high-quality clinical trials. A 2012 review and meta-analysis in the American Journal of Clinical Nutrition concluded "vitamin D3 is more efficacious at raising serum 25(OH)D concentrations than is vitamin D2." (5).

A 2019 study published in the Journal of Clinical Endocrinology and Metabolism by Martineau, et al. (6) concluded that vitamin D2 administration reduced vitamin D3 metabolism and was less effective than vitamin D3 in elevating total vitamin D levels. 

The clinical significance of these findings is not yet fully understood. We know pharmacologic doses of both vitamin D2 and D3 are able to elevate vitamin D levels well into the normal range (6), and intermittent high doses of vitamin D2 has been shown to adequately treat and prevent recurrence of vitamin D deficiency (7). In addition, fortification of orange juice with either vitamin D2 or D3 is equally effective as oral supplements in improving vitamin D status (8). More research is needed to answer these questions.

Call Woodbury Endocrinology and Diabetes Clinic today at (612) 425-0958 to schedule an appointment with Dr. Alfonso if you have vitamin D deficiency, osteopenia, osteoporosis, hyperparathyroidism, hypercalcemia, or just wondering if you should be on vitamin D supplements.

Sources:

1. Nutrients. 2017 Aug; 9(8): 849.

2. JAMA. 1930;95(5):316-323.

3. Am JClin Nutr 2006;84:694.

4. J Clin Endocrinol Metab, March 2011, 96(3):E447–E452.

5. Am J Clin Nutr 2012;95:1357–64.

6. J Clin Endocrinol Metab. 2019 Dec 1;104(12):5831-5839.

7. Arch Intern Med. 2009 Oct 26;169(19):1806-8. 

8. Am J Clin Nutr. 2010 Jun;91(6):1621-6.